Sorbaria sorbifolia Seeds | Arborea

Creamy white flower plumes rising above fern-like pinnate leaves of false spiraea — False Spiraea (*Sorbaria sorbifolia*): Rosaceae, eastern Asia.

LATIN NAME: Sorbaria sorbifolia

COMMON NAME: False Spiraea

Plant Profile

False spiraea is not a fern, though it is often described as one: it is a suckering deciduous shrub of one to two metres whose pinnate leaves are made of up to twenty-one narrow leaflets, giving it the look of a large fern until the cream plumes of midsummer arrive. The flower panicles are upright, dense and full of small white flowers, and they last for weeks. It is native to eastern Asia, and it spreads by underground runners into a thicket, which is either its virtue or its vice. The stems are straight and brown, and the winter silhouette is a thicket of clean, vertical lines.

Science & Biotechnology

The species is a shrub in Rosaceae, in the sorbaria tribe, and its fern-like leaves are a case of convergent appearance rather than relationship. It is a vigorous coloniser, and in north-eastern North America and parts of Europe it has escaped into damp woodland and riverbanks, where its dense suckering stands crowd out native ground flora; several jurisdictions list it as invasive. Its chemistry includes sorbitol and flavonoids, and it has been screened for antioxidant activity, but it has no established medicinal use. The cultivar Sem is a tetraploid and is much more compact than the type, which is why it has largely replaced it in gardens. Its seed is light and has no wing at all, which is why it spreads by root rather than by wind.

Uses & Benefits

In the garden it is a bold foliage shrub for a large informal planting, a waterside bank or a wild corner, and the cultivar Sem is a compact, reddish-flushed form that behaves far better in a small space. The plumes are good for cutting. It is also a useful plant for stabilising wet banks, which is precisely why it can spread. It should not be planted near sensitive natural areas, and the suckers need containing. The dried seed heads hold their shape through winter, which is a small argument in its favour. The flowers are also visited by a wide range of small bees and flies, which is one reason it is planted in wildlife gardens.

Growing from Seed

Sow the seed in autumn or spring on a moist mix; it needs light and germinates in two to four weeks at eighteen to twenty degrees. The seedling is fast and will flower in its second or third year. Plant out in sun or part shade, in any moist soil, and give it a root barrier or a mown strip if the suckering is to be controlled. Cut the oldest stems to the ground in late winter to keep the thicket young and the plumes large. It is indifferent to soil and water, which is another way of saying it is hard to stop.

Our Take

A fern that is really a shrub, spectacular in a big wet garden and a thug anywhere it can run. Buy the compact form, and put a barrier in the ground before you plant it.

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